Transition Networks, Inc.
S4224 Web User Guide
33595 Rev. C
Page 665 of 669
U
UDP
UDP (
U
ser
D
atagram
P
rotocol) is a communications protocol that uses the Internet Protocol (IP) to exchange
the messages between computers. UDP is an alternative to the Transmission Control Protocol (TCP) that uses
the Internet Protocol (IP). Unlike TCP, UDP does not provide the service of dividing a message into packet
datagrams, and UDP doesn't provide reassembling and sequencing of the packets. This means that the
application program that uses UDP must be able to make sure that the entire message has arrived and is in the
right order. Network applications that want to save processing time because they have very small data units to
exchange may prefer UDP to TCP.
UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different
user requests and, optionally, a checksum capability to verify that the data arrived intact. Common network
applications that use UDP include the Domain Name System (DNS), streaming media applications such as
IPTV, Voice over IP (VoIP), and Trivial File Transfer Protocol (TFTP).
UNI
(User Network Interface) the physical interface or port that is the demarcation between the customer and the
service provider/Cable Operator/Carrier/MSO per MEF 4.
UNI-C
UNI – Customer per MEF 4. A compound architectural component on the Subscriber side of the UNI that
represents all the functions required to connect a subscriber to a MEN (per MEF 27).
UNI-N
UNI – Network per MEF 4. A compound functional element used to represent all of the functional elements
required to connect a MEN to a MEN subscriber implementing a UNI C. The functional elements within the
Customer Edge that supports the MEN Subscriber’s technical capabilities and compliance to the UNI
specification. A set of one or more functional elements that supports the MEN Service Provider’s technical
capabilities and compliance to the UNI specification. (Per MEF 27.)
Unicast address
In IPv6, an identifier for a single interface. A packet sent to a unicast address is delivered to the interface
identified by that address.
Uniform Model
One of three different Diffserv tunneling models defined in RFC 3270, and which define e.g. inheritance of TTL
and EXP/TC in the label stack during push and pop. TTL inheritance is defined in RFC 4343. See also "Pipe
Model" and "Short Pipe Model".
UPnP
UPnP (
U
niversal
P
lug a
n
d
P
lay). The goals of UPnP are to allow devices to connect seamlessly and to simplify
the implementation of networks in the home (data sharing, communications, and entertainment) and in
corporate environments for simplified installation of computer components.
Upper layer
In IPv6, a protocol layer immediately above IPv6. Examples are transport protocols such as TCP and UDP,
control protocols such as ICMP, routing protocols such as OSPF, and internet or lower-layer protocols being
"tunneled" over (i.e., encapsulated in) IPv6 such as IPX, AppleTalk, or IPv6 itself.
User Priority
User Priority is a 3-bit field storing the priority level for the 802.1Q frame. It is also known as PCP.
